The only thing I do differently for my males is top off their weekly rat offering at smalls vs. mediums for females. Beyond that I don't purposely hold them to some sort of target weight as they tend to self-regulate smaller than females on their own. It's much more important for them to have a solid body shape than define themselves by a number. I have had a few males on the larger side, but they are the exception rather than the rule and have bred just fine for me. Maybe they forgot to read the manual?